During the 2020 growing season, Dr. Eric Hunt of Atmospheric and Environmental Research, Inc. will be providing weekly updates of the soil moisture index (SMI) from the Noah-MP land surface model in the NASA LIS framework for the eastern 3/4 of the U.S. where row-crop agriculture is more common. The Evaporative Stress Index (ESI) will be included in our analysis later this season. The analysis is intended to provide the larger agricultural and meteorological communities insight as to areas where soil moisture is excessive or deficient compared to average for that location and what that may mean for impacts. It is my goal that these maps can be an early warning signal for flash drought development or where flash flooding could be likely in the coming week if heavy precipitation materializes. Please be advised that the SMI should be viewed as complementary, not a substitute, to the U.S. Drought Monitor (USDM) and that declarations of drought or flash flood potential for a particular location should never be based on the SMI alone.
This blog post was partially supported by NASA grant 80NSSC19K1266.
Figure 1. The Soil Moisture Index (SMI) for the 7-day period ending 30 April 2020 (top left) and 2 April 2020 (bottom left). On the right hand side are the grid points where the SMI is at or below -4.0 (top right, red) and grid points where the SMI is at or above 4.0 (top right, green). Results are based on output from the 0-1 m (surface to 3.23 feet) layers in the Noah-Multiparameterization (Noah-MP) land surface model. Noah-MP is run in the NASA Land Information System (LIS) framework with the North American Land Data Assimilation Version 2 (NLDAS-2) forcing dataset. The SMI calculation is based on the soil moisture index created in Hunt et al. (2009) such that ‘5’(dark green) is the wettest and ‘-5’ (dark red) the driest for the period of record. The period of record used calculate the SMI for the current map is 1979-present.
Table 1 (above) shows the median SMI value from the current map, 30 days ago, and one year ago at this time.
Narrative:
Recent weather has been favorable across most of the Corn Belt for planting with 51 percent of U.S. corn planted according to the latest Crop Progress Report, which is well ahead of last year at this time. Several states are above 50 percent planted, including Illinois (56 percent), Iowa (78 percent), Minnesota (76 percent), and Nebraska (61 percent). The Eastern Corn Belt is lagging these states but the situation for planting is much better than 2019.
Most of the eastern U.S. has seen improvement over the last month (Fig. 1), especially across southern Georgia and Florida where drought has recently been eliminated from the U.S. Drought Monitor (Fig. 3). The opposite is true over much of the north central U.S. where the SMI has dropped to negative median values (based on 1979-2020) for four of the five regions analyzed (Fig 2.) The largest degradation has been over the northern two-thirds of lower Michigan and across much of Nebraska, Iowa, and Minnesota.
For now, I am optimistic the current drier conditions may end up being favorable for crops later in the season. But that is contingent upon having some periods of decent precipitation later in May and June. The analogs would suggest as much is likely, which you can read about in our May Crop Forecast Update that will be released for subscribers next week.
